1. Field of the Invention
The invention relates to a split core insulating cover and locking apparatus for holding two split cores in position around a conductor whose current load is to be determined.
2. Description of Related Art
Submetering of electricity provides the opportunity to conserve energy consumption by monitoring individual circuits. Submetering also has economic advantages such as branch circuit metering for two or more tenants or loads on the same subpanel. However, practical utilization of submetering requires monitoring equipment that does not require interconnection or severing of the circuits to be measured. Use of a ferrous core with a pick-up transformer to encircle a conductor and measure current flow is well known in the art. Current flowing through the conductor generates a magnetic flux in the encircling core. A pick-up transformer encircles or is wound onto the core. The windings of the pick-up transformer must correspond to the direction of current flow in the measured conductor. The flux in the core generates a voltage in the pick-up transformer that is representative of the current flow in the measured conductor.
One present method of fastening the split cores to the conductor is to place the cores around the conductor with the pick-up transformer attached directly around the cores. The split cores are then strapped together using common plastic ties such as made by the Panduit Corporation. The split cores are not insulated from the surrounding electrical components. The proper orientation of the pick-up transformer must be obtained by correctly determining current flow and the direction of the generated magnetic flux relative to he windings in the pick-up transformer.
U.S. Pat. No. 4,286,213 describes a one piece U-shaped bracket which functions as a core. A pin fastens a pick-up transformer between the legs of the bracket thus encircling the conductor to be monitored. The bracket is not insulated on its outside surface. Further, the core does not completely surround the conductor.
A four-part laminated core with the pick-up transformer integrally wound onto one or more parts of the core is described in U.S. Pat. No. 3,883,835. Four corner brackets and four tubes are used to surround the core and hold it together. Bolts or similar fasteners are used to assemble the four parts of the core cover together. Various current load ranges must be matched to appropriately sized pick-up transformers. A core assembly with an integrally wound pick-up transformer can be used for only one current load range.
U.S. Pat. No. 4,408,175 discloses a two-part hinged plastic housing for enclosing a pick-up transformer. The device is designed to fasten a pick-up transformer directly to the conductor without the use of a ferromagnetic core. Non-magnetic stainless screws are used to lock the two halves of the housing around the conductor.
U.S. Pat. Nos. 4,471,300; 4,258,348; 4,048,605; 3,314,009; 2,709,800 disclose typical hinged split-core encircling devices with pick-up transformers. None of the disclosures provide a means for covering the core and locking the core and its pick-up transformer onto the conductor.
U.S. Pat. Nos. 4,234,863 and 4,558,271 are of general interest only to the invention.
An insulating cover for a split core, capable of locking the core and its pick-up transformer around the conductor without screws, bolts or tie straps does not appear to be found in the prior art. A simple two piece cover, inexpensive to manufacture, and capable of being easily fastened and removed is not shown. Means for insuring proper orientation of a pick-up transformer relative to the current flow in the monitored conductor is not disclosed.